diff --git a/src/docs/spec-intro.md b/src/docs/spec-intro.md
index 1dacae7a..89042e83 100644
--- a/src/docs/spec-intro.md
+++ b/src/docs/spec-intro.md
@@ -27,3 +27,5 @@ Throughout the specification, the following IRI prefix names are used:
 | semapv      | https://w3id.org/semapv/vocab/ |
 | skos        | http://www.w3.org/2004/02/skos/core# |
 | sssom       | https://w3id.org/sssom/ |
+| xsd         | http://www.w3.org/2001/XMLSchema# |
+| linkml      | https://w3id.org/linkml/ |